1. Field of the Invention
Embodiments of the present invention generally relate to downhole telemetry systems, and more particularly to wired drill pipe that conveys data and/or power between one or more downhole locations within a borehole and the surface.
2. Description of the Related Art
For the past several decades, engineers have worked to develop apparatuses and methods to effectively transmit information from components located downhole on oil and gas drilling strings to the ground's surface. Part of the difficulty of this problem lies in the development of reliable apparatus and methods for transmitting information from one drill string component to another, such as between sections of drill pipe. The goal is to provide reliable information transmission between downhole components stretching thousands of feet beneath the earth's surface, while withstanding hostile wear and tear of subterranean conditions.
Measurement While Drilling (MWD) and Logging While Drilling (LWD) systems derive much of their value from the ability to provide real-time information about downhole conditions near the drill bit. Oil companies use these downhole measurements to make decisions during the drilling process, e.g., to provide input or feedback information for sophisticated drilling techniques such as the GeoSteering system developed by Schlumberger. Such techniques rely heavily on instantaneous knowledge of many variables such as characteristics of the formation that is being drilled, weight on drill bit, depth, azimuth, drill speed, drill penetration rate, bit whirl, drill bit location within the formation, downhole pressure, downhole temperature, etc. Accordingly, the industry continues to develop new real-time (or near real-time) measurements capabilities, including imaging-type measurements with high data content and bit rate.
In an effort to provide solutions to this problem, engineers have developed a technology known as mud pulse telemetry. Data transmission between downhole and surface locations with mud pulse telemetry involves using the drill string is used to convey modulated acoustic waves in the drilling fluid. Data transmission rates using mud-pulse telemetry lie in the range of 1-6 bits/second. Such slow rates are incapable of transmitting the large amounts of data that are typically gathered with a LWD string. Additionally, in some cases (e.g., when using foamed drilling fluid), mud-pulse telemetry does not work at all. As a result, it is not uncommon for some or all of the data collected by MWD/LWD systems to be stored in downhole memory and downloaded when the systems return to the surface. This delay significantly reduces the value of the data for real-time or near real-time applications. Also, there is a significant risk of data loss, for example, if the MWD/LWD tool(s) are lost in the borehole.
Moreover, at the slow data rate mud-pulse telemetry offers, data resolution is typically poor, preventing a driller from making crucial decisions in real time. Since drilling equipment is often rented and very expensive, even slight mistakes incur substantial expense. Part of the expense can be attributed to time-consuming operations that are required to retrieve downhole data or to verify low-resolution data transmitted to the surface by mud pulse telemetry. Often, drilling or other procedures are halted while crucial data is gathered.
In an effort to overcome limitations imposed by mud pulse telemetry systems, reliable connections are needed to transmit information between components in a drill string. As a result, a number of new and/or modified telemetry techniques for use with current MWD/LWD systems as well as other real time data collection systems have been proposed or attempted with varying degrees of success.
For example, a new telemetry system having a communication channel within drill pipe, often referred to as wired drill pipe (“WDP”), has been proposed. WDP has a cable with a coupler at each joint, such as a magnetic inductive coupler disclosed in U.S. Pat. Nos. 6,670,880 and 6,844,498. Another such system using a toroidal inductive coupler has been disclosed in U.S. Pat. Nos. 6,641,434 and 7,413,021. However, these systems rely on double shouldered premium tool joint connections, where a primary external and secondary internal shoulder are load bearing shoulders and resist the stresses associated with high torque make up of tool joints. This is due in part to the targeted market for WDP such as extended reach wells that require high connection torque and thus the premium connection tool joints. Additionally, some of the WDP systems require high contact pressure for best efficiency and the internal shoulder is one of the positions that house various components of WDP systems.
However, the high torque requirement sometimes is only necessary in the drill pipe section of a drill string, where the bottom hole assembly (BHA) section may require standard API torques. Various downhole components located in the BHA may include LWD tools, drill collars, and jars. Additionally, many types of drill pipe and drilling applications simply do not need premium tool joint connections and are only required to handle standard API torques. Most of these types of applications have non-double shouldered tool joints, and thus no shoulder to house some of the components used in WDP systems. Many of the elements located in the BHA section of the drill string as well as repeaters located throughout the drill string utilize non-double shouldered connections. Thus, there is a need to connect WDP having double shouldered connections to WDP having single shouldered connections.